Gas blowing plug and method for manufacturing the same

Abstract

To increase a gas flow rate compared with the conventional plugs.SOLUTION: A gas blowing plug comprises: a core body part 2 made of a porous refractory; an outer circumferential part 3 made of a dense refractory and at least partially surrounding the core body part 2; a gas pool 5 in contact with the core body part 2; and a gas feed pipe 6 fluid-connected to the gas pool 5. A clearance 7 at least partially extending to a space between the core body part 2 and the outer circumferential part 3 and not contacted with the gas pool 5 is provided, and the clearance 7 is opened at a tip face 12.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a gas injection plug and a method for manufacturing the gas injection plug. [Background technology]

[0002] A commonly used method for stirring molten metal in a vessel for handling molten metal, such as a ladle or a crucible, is to inject gas into the bottom of the vessel to fluidize the molten metal with the gas. An example of a gas-injecting plug attached to the bottom of the vessel for this purpose is a gas-injecting plug 8, as shown in FIG. 8 , which includes a core portion 2 made of a porous refractory, an outer peripheral portion 3 made of a dense refractory and surrounding the core portion 2, and an air inlet pipe 6 for supplying gas to the core portion 2. In this gas-injecting plug 8, the core portion 2 functions as a gas flow path, and gas supplied from the air inlet pipe 6 passes through the core portion 2 and is released into the vessel from the tip surface 22 (path A). This type of gas-injecting plug is sometimes referred to as a porous plug.

[0003] In porous plugs, molten metal adheres to the tip and penetrates the pores of the porous refractory, causing the gas path to become clogged. This phenomenon causes the gas flow rate through the porous plug to gradually decrease with repeated operation. Porous plug blockage can be eliminated by oxygen cleaning, in which oxygen is sprayed onto the tip. However, this process causes the refractory to dissolve, and repeated oxygen cleaning shortens the life of the porous plug. Therefore, to extend the life of a porous plug, it is necessary to make it more difficult for molten metal to adhere to the tip and reduce the frequency of oxygen cleaning. Various structures are being investigated to achieve this.

[0004] For example, Japanese Utility Model Laid-Open Publication No. 3-68958 (Patent Document 1) discloses a porous plug in which a porous joint is provided around a plug body made of a porous refractory material. According to the porous plug of Patent Document 1, when the plug body becomes clogged, the joint undergoes erosion, eroding the lower part of the clogged portion (wetted layer), and leading to peeling of the clogged portion, so that the plug is automatically cleared of clogged state.

[0005] Furthermore, Japanese Patent Laid-Open Publication No. 9-194927 (Patent Document 2) discloses a plug in which, instead of the core portion made of porous refractory material used in general porous plugs, dense refractory rods are arranged in a staggered pattern and the joints between the refractory rods are used as gas flow paths. According to the plug in Patent Document 2, the cross-sectional area of ​​each gas flow path is small, making it difficult for molten metal to enter and preventing blockages. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Utility Model Application Publication No. 3-68958 [Patent Document 2] Japanese Patent Application Publication No. 9-194927 Summary of the Invention [Problem to be solved by the invention]

[0007] Although the technology of Patent Document 1 reduces the need for maintenance work when clogging occurs, the gas flow rate under normal conditions is the same as that of the technology prior to Patent Document 1. Furthermore, with the technology of Patent Document 2, the side surfaces of the outermost refractory rods are blocked by the dense refractory material on the periphery, making it difficult to increase the gas flow rate. As such, conventional plugs have room for improvement in terms of increasing the gas flow rate.

[0008] Therefore, there is a need to develop a gas injection plug that can increase the gas flow rate compared to conventional plugs, and a method for manufacturing the same. [Means for solving the problem]

[0009] The gas-blowing plug according to the present invention comprises a core portion made of a porous refractory material, an outer peripheral portion made of a dense refractory material at least partially surrounding the core portion, a gas pool in contact with the core portion, and an air supply pipe in fluid communication with the gas pool, and a gap is provided between the core portion and the outer peripheral portion at least partially extending and not in contact with the gas pool, and a tip surface 、 The gap is open and the tip of the core portion is exposed. It is characterized by:

[0010] With this configuration, gas supplied from the air inlet pipe flows through two paths before it leaves the tip of the gas blowing plug: one via the tip face of the core portion, and the other via the side face of the core portion and the gap. The former path is also present in gas blowing plugs of the prior art, but the latter path is not present in gas blowing plugs of the prior art. Therefore, the above configuration increases the gas flow path by the amount of the latter path compared to the prior art. This can increase the gas flow rate compared to conventional plugs.

[0011] Further, a method for manufacturing a gas-blowing plug according to the present invention comprises a first step of forming a preform for a gas-blowing plug and a second step of firing the preform, wherein the first step comprises a step of forming a core portion of the preform using a porous refractory material, a step of forming an outer peripheral portion of the preform using a dense refractory material, and a step of disposing a combustible material between the core portion and the outer peripheral portion of the preform, and the second step comprises burning away at least a part of the combustible material, and in the step of disposing the combustible material, the combustible material is disposed so as to be exposed at a tip end surface of the preform but not exposed at a base end surface of the preform. The gas injection plug has a gap formed by burning off the combustible material at the tip end surface, and the tip end of the core portion is exposed. It is characterized by:

[0012] According to this configuration, the method for providing the gap is relatively simple, and therefore, a plug having an increased gas flow rate compared to conventional plugs can be obtained without impairing productivity.

[0013] Preferred embodiments of the present invention will be described below, but the scope of the present invention is not limited to the preferred embodiments described below.

[0014] In one aspect, the gas injection plug according to the present invention preferably further comprises a metal case that at least partially surrounds the outer circumferential portion.

[0015] This configuration facilitates installation of the air supply pipe and also provides a support for removing and replacing the gas injection plug.

[0016] In one aspect of the gas blowing plug according to the present invention, the width of the gap is preferably 0.10 mm or more and 0.50 mm or less.

[0017] According to this configuration, it is easy to ensure gas flow rates in both the path via the tip surface of the core portion and the path via the side surface and gap of the core portion, so that both paths are less likely to become clogged.

[0018] In one embodiment of the method for producing a gas blowing plug according to the present invention, the combustible material is preferably in the form of a wire, a rod, a sheet, or a combination thereof.

[0019] According to this configuration, it is possible to easily form a gap with a uniform thickness.

[0020] Further features and advantages of the present invention will become more apparent from the following description of exemplary and non-limiting embodiments, which is given with reference to the drawings. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 2 is a longitudinal sectional view of the gas injection plug according to the embodiment. [Figure 2] FIG. 2 is a top view of a gas injection plug according to an embodiment. [Figure 3] FIG. 2 is a cross-sectional view taken along line III-III in FIG. [Figure 4] 1A to 1C are diagrams illustrating a procedure for manufacturing a gas injection plug according to an embodiment. [Figure 5] 1A to 1C are diagrams illustrating a procedure for manufacturing a gas injection plug according to an embodiment. [Figure 6] 1A to 1C are diagrams illustrating a procedure for manufacturing a gas injection plug according to an embodiment. [Figure 7] 1A to 1C are diagrams illustrating a procedure for manufacturing a gas injection plug according to an embodiment. [Figure 8] FIG. 1 is a longitudinal sectional view of a gas injection plug according to the prior art. [Figure 9] FIG. 10 is a diagram showing the results of an air flow test. DETAILED DESCRIPTION OF THE INVENTION

[0022] Embodiments of a gas-blowing plug and a method for manufacturing the same according to the present invention will be described with reference to the drawings. In the following, an example will be described in which the gas-blowing plug according to the present invention is applied to a gas-blowing plug 1 (hereinafter simply referred to as "plug 1") installed at the bottom of a molten metal refining vessel.

[0023] [Plug configuration] The plug 1 according to this embodiment comprises a core portion 2, an outer peripheral portion 3 surrounding the core portion 2, and a metal case 4 accommodating the core portion 2 and the outer peripheral portion 3 (FIG. 1). The base end surface 21 of the core portion 2 contacts a gas pool 5, and an air supply pipe 6 fluidly communicating with the gas pool 5 is welded to the metal case 4. The plug 1 is a porous plug that serves to discharge gas supplied from the base end 11 side from the front end surface 12, and the core portion 2 made of a porous refractory material functions as a gas flow path. A gap 7 is provided between the core portion 2 and the outer peripheral portion 3, and the gap 7 opens to the front end surface 12 of the plug 1.

[0024] The leading end of the plug 1 refers to the side exposed to the inside of a molten metal refining vessel when the plug 1 is in use (the upper side in FIG. 1), and the base end of the plug 1 refers to the side facing the outside of the molten metal refining vessel when the plug 1 is in use (the lower side in FIG. 1). Therefore, the leading end face 12 of the plug 1 is exposed to molten metal when in use.

[0025] The core portion 2 is made of a porous refractory. The porous refractory may be any porous refractory commonly used in the art, such as a high-alumina or magnesia refractory. That is, the porous refractory is a press-molded product that may contain metal oxides such as alumina, magnesia, and chromia. The porous refractory may also contain carbon, mullite, a zirconia compound, a boron compound, clay, and the like.

[0026] The shape of the core portion 2 is not particularly limited and may be any shape, such as a truncated cone or a truncated pyramid. In this embodiment, as an example, an upper portion 24 of the core portion 2 is truncated cone, and a lower portion 25 is truncated quadrangular pyramid (FIGS. 2 and 3). The tip surface 22 of the core portion 2 is circular.

[0027] The outer peripheral portion 3 is made of a dense refractory material and is provided in a manner that surrounds the core portion 2 in the circumferential direction. The dense refractory material that constitutes the outer peripheral portion 3 can be a dense refractory material commonly used in the art, such as a high-alumina, alumina-magnesia, or alumina-spinel refractory. That is, the dense refractory is a poured product that can contain metal oxides such as alumina, magnesia, or spinel. The dense refractory may also contain alumina cement, silica flour, metal powder, a dispersant, or the like.

[0028] In this embodiment, an example is shown in which the outer circumferential portion 3 has a truncated cone shape. Correspondingly, the front end surface 12 and cross section of the plug 1 are circular (FIGS. 2 and 3). The cross-sectional shapes of the core portion 2 and the outer circumferential portion 3 may be different, or may be the same (e.g., circular and circular).

[0029] The metal case 4 is a metal case that houses the core portion 2 and the outer peripheral portion 3. There are no particular limitations on the metal that constitutes the metal case 4, and it can be, for example, SPCC, SUS304, or the like. The metal case 4 is open on the tip side of the plug 1, so that the core portion 2 and the outer peripheral portion 3 are exposed at the tip surface 12 of the plug 1. On the other hand, the side surfaces and base end sides of the core portion 2 and the outer peripheral portion 3 are enclosed by the metal case 4.

[0030] A gas pool 5 is provided between the metal case 4 and the base end surface 21 of the core portion 2 and the base end surface 31 of the outer peripheral portion 3. The gas pool 5 is a space that does not contain any substantial components, and functions as a space for the gas that flows in from the air supply pipe 6 to diffuse laterally (in a direction intersecting the longitudinal direction of the plug 1).

[0031] An air supply pipe 6 that is in fluid communication with the gas pool 5 is welded to the metal case 4. The air supply pipe 6 is a metal pipe, and the metal may be, for example, SGP, STPG370, etc. The metal that constitutes the metal case 4 and the metal that constitutes the air supply pipe 6 may be the same metal, or may be different metals to the extent that they can be welded to each other.

[0032] In the plug 1 according to the present embodiment, a gap 7 is provided between the upper portion 24 of the core portion 2 and the outer peripheral portion 3. On the other hand, no gap is provided between the lower portion 25 of the core portion 2 and the outer peripheral portion 3. Therefore, the gap 7 is open to the front end face 12 of the plug 1 and extends along the core portion 2 and the outer peripheral portion 3, but is not in contact with the gas pool 5 (FIGS. 1 to 3).

[0033] Gas supplied to the plug 1 from a gas source (not shown) reaches the gas pool 5 through the gas supply pipe 6, diffuses in the radial direction of the plug 1 in the gas pool 5, and enters the pores of the core portion 2 from the base end face 21 of the core portion 2. The gas further travels through the core portion 2, and a portion of the gas flows into the interior of the molten metal refining vessel from the front end face 22. Another portion flows into the gap 7 from the side face 23 and then into the interior of the molten metal refining vessel via the gap 7. As described above, in the plug 1 according to this embodiment, in addition to path A via the front end face 22 (a path that also exists in the conventional plug 8 (FIG. 8)), path B via the side face 23 and the gap 7 is additionally provided as a path for the gas to flow into the interior of the molten metal refining vessel. This enables the permeability of the plug 1 to be improved.

[0034] In this embodiment, the width of the gap 7 is set to 0.30 mm. When the width of the gap 7 is 0.10 mm or more, as in this example, gas easily flows into the gap 7, making it easier to ensure a sufficient gas flow rate throughout the plug 1. When the width of the gap 7 is 0.50 mm or less, molten metal does not easily flow into the gap 7, making it easier to avoid clogging of the gap 7. The width of the gap 7 is more preferably 0.15 mm or more, and even more preferably 0.18 mm or more. The width of the gap 7 is more preferably 0.45 mm or less, and even more preferably 0.40 mm or less.

[0035] Since the gap 7 is provided in a manner that does not contact the gas pool 5, the gases in both paths A and B pass through the core portion 2. This makes it easy to ensure a sufficient gas flow rate in both paths A and B, and can suitably prevent the adhesion of molten metal to the entire front edge face 12 of the plug 1. In contrast, if the gap 7 were in contact with the gas pool 5, most of the gas would bypass the core portion 2 and flow into the molten metal refining vessel through the gap 7, which would significantly reduce the gas flow rate at the front edge face 22 and make it easier for molten metal to adhere to the front edge face 22.

[0036] [Plug manufacturing method] Next, a description will be given of a method for manufacturing the plug 1. The method for manufacturing the plug 1 includes a first step of forming a preform 1a for the plug 1, a second step of firing the preform 1a, and a third step of housing the fired body obtained in the second step in a metal case 4. The first step is further divided into a first step of forming a core portion 2a of the preform 1a, a second step of surrounding the core portion 2a of the preform 1a with a combustible material 7a, and a third step of forming an outer peripheral portion 3a of the preform 1a.

[0037] (1) First step In the first step of the first process, a core portion 2a of the preform 1a is formed using a porous refractory (FIG. 4). The porous refractories used here are as listed above, and the shape of the core portion 2a of the preform 1a is determined so that the core portion 2a of the plug 1 will have the desired shape after firing the preform 1a. Tools, auxiliaries, and the like that are typically used for preforming porous refractories can be used.

[0038] In the second step of the first process, the core portion 2a of the preform 1a is surrounded by a combustible material 7a (FIG. 5). The combustible material 7a used here is a substance that burns at the firing temperature (e.g., 500°C or lower) of the porous refractory constituting the core portion 2 and the dense refractory constituting the outer peripheral portion 3 of the plug 1. The position and size of the combustible material 7a are determined so that the voids formed when the combustible material 7a is burned away during firing of the preform 1a will have the desired shape of the voids 7. In particular, the combustible material 7a is aligned flush with the front end surface 22a of the core portion 2a, but does not reach the base end surface 21a of the core portion 2a, so that the voids 7 open to the front end surface 12 of the plug 1 and do not come into contact with the gas pool 5. It is preferable that the combustible material 7a be in the shape of a wire, rod, or sheet, or a combination thereof, because this facilitates the formation of voids 7 of uniform thickness.

[0039] In the third step of the first process, the outer peripheral portion 3a of the preform 1a is formed using a dense refractory (FIG. 6). In this embodiment, the third step is performed after the second step described above. Therefore, in the portion where the core portion 2a is surrounded by the combustible material 7a, the outer peripheral portion 3a is formed so as to further surround the combustible material 7a. The dense refractories used here are as listed above, and the shape of the outer peripheral portion 3a of the preform 1a is determined so that the outer peripheral portion 3a of the plug 1 will have the desired shape after firing the preform 1a. Note that tools, auxiliaries, and the like that are typically used for preforming dense refractories may be used.

[0040] Through the above three steps, a preform 1a is obtained, which includes a core portion 2a, an outer peripheral portion 3a, and a combustible material 7a. As is clear from the above procedure, the second step is a step of disposing the combustible material 7a between the core portion 2a and the outer peripheral portion 3a of the preform 1a.

[0041] (2)Second process The second step is a step of firing the preform 1a. Known firing equipment and firing conditions can be used and are determined taking into consideration the types of porous refractories and dense refractories used, the types of secondary materials such as additives and auxiliaries, and the dimensions of the preform 1a. When the preform 1a is fired, the combustible material 7a is burned away, resulting in a fired body 1b having voids 7 (FIG. 7). That is, the second step involves burning away at least a portion of the combustible material 7a.

[0042] (3) Third step The third step is a step of housing the sintered body 1b obtained in the second step in a metal case 4. The third step can be carried out by a method that is usually carried out when housing a sintered body made of a refractory material in a metal case in a manufacturing method of a porous plug.

[0043] Other Embodiments Finally, other embodiments of the gas blowing plug and the method of manufacturing the gas blowing plug according to the present invention will be described. Note that the configurations disclosed in the following embodiments can be applied in combination with the configurations disclosed in other embodiments, provided that no contradictions arise.

[0044] In the above embodiment, an example has been described in which the gap 7 is provided around the entire periphery of the upper portion 24 of the core portion 2. However, in the gas injection plug according to the present invention, the gap need only extend at least partially between the core portion and the outer periphery, and does not have to be shaped to surround the core portion as in the above example.

[0045] In the above embodiment, the plug 1 is described as having a metal case 4. However, the gas blowing plug according to the present invention may not have a metal case. Furthermore, when a metal case is provided, the entire outer periphery may be housed in the metal case as in the above embodiment, or only a portion of the outer periphery may be housed in the metal case.

[0046] In the above embodiment, the method for manufacturing the plug 1 has been described as an example in which the preform 1a is obtained by performing the following steps in this order: a first step of forming the core portion 2a of the preform 1a; a second step of surrounding the core portion 2a of the preform 1a with a combustible material 7a; and a third step of forming the outer periphery 3a of the preform 1a. However, the order in which the steps are performed is not limited as long as the first step of the method for manufacturing a gas-blowing plug according to the present invention obtains a preform in which a combustible material is disposed between the core portion and the outer periphery.

[0047] Regarding other configurations, it should be understood that the embodiments disclosed in this specification are illustrative in all respects and that the scope of the present invention is not limited thereby. Those skilled in the art will easily understand that appropriate modifications are possible without departing from the spirit of the present invention. Therefore, other embodiments modified without departing from the spirit of the present invention are naturally included in the scope of the present invention. [Example]

[0048] The present invention will be further described below with reference to examples, but the present invention is not limited to these examples.

[0049] [Air flow test] Examples and Comparative Examples As Example 1, a plug having the cross-sectional shape shown in FIG. 1 was manufactured. As a comparative example, a plug having the cross-sectional shape shown in FIG. 8 was manufactured. The porous refractory constituting the core portion and the dense refractory constituting the outer peripheral portion of both plugs were the same. Specifically, the porous refractory had a composition of 89% alumina, 7% silica, and 2% chromia, and the dense refractory had a composition of 91% alumina and 7% magnesia. The overall length of the refractory portions (core portion and outer peripheral portion) of the plug was 300 mm. The upper portion of the core portion was frustum-shaped, with a length of 240 mm, an upper diameter of 80 mm, and a lower diameter of 120 mm. The lower portion had a square cross-section in the shape of a truncated pyramid, with a length of 60 mm, an upper side of 80 mm, and a lower side of 100 mm. In the plug of Example 1, the width of the gap was 0.3 mm. On the other hand, the plug of the comparative example had a structure in which the core portion and the outer periphery were in close contact with each other, and no gap was provided.

[0050] (evaluation) Each plug of the Example and Comparative Examples was connected to a gas source (not shown), and gas was supplied at a pressure ranging from 0.1 to 0.3 MPa to measure the gas flow rate (units: L / min). The relationship between pressure and flow rate for each plug is shown in Figure 9. It was found that when the plug of Example 1 was used, the gas flow rate was improved compared to when the plug of Comparative Example was used, within the gas supply pressure range of 0.1 to 0.3 MPa.

[0051] [Actual use test] Examples and Comparative Examples In addition to the above-mentioned Example 1 and Comparative Example, Examples 2 to 8 were produced, each of which had the same structure as the plug of Example 1, except that the width of the gap was changed within the range of 0.10 to 0.70 mm. The specific values ​​of the width of the gap in each Example are shown in Table 1 below.

[0052] (evaluation) Each nozzle of Examples 1 to 8 and the Comparative Example was attached to a 300-ton ladle and used in batch casting of steel. At the end of each batch, if the flow rate of gas supplied to the gas-blowing plug at a pressure of 0.1 MPa was less than 150 L / min, oxygen cleaning was performed, and if the height of the gas-blowing plug was 60 mm or less, the plug was deemed unusable. The number of batches up to the point where each plug was deemed unusable was recorded (Table 1). In Examples 1 to 8, an extension of the lifespan was observed compared to the Comparative Example (a nozzle according to the prior art) without a gap. The extension of the lifespan was particularly remarkable in Examples 1 to 7, in which the width of the gap was 0.10 mm or more and 0.50 mm or less.

[0053] Table 1: Real-world testing [Table 1] [Industrial Applicability]

[0054] The present invention may be utilized, for example, as a gas injection plug located at the bottom of a molten metal refining vessel. [Explanation of symbols]

[0055] 1: Gas injection plug 11: Base end of gas injection plug 12: Tip surface of gas injection plug 2:Core part 21: Base end surface of core part 22: Tip surface of core part 23: Side of the core part 3:Outer part 31: Base end surface of outer periphery 4: Metal case 5: Gas pool 6: Air supply pipe 7 :Void 1a: Preform 2a: Core part of preform 21a: Base end surface of the core portion of the preform 22a: Tip surface of the core part of the preform 3a: Peripheral portion of preform 7a :Flammable materials 8: Gas injection plug (conventional technology) A, B: Gas path

Claims

1. a core portion made of a porous refractory material; an outer peripheral portion made of a dense refractory material at least partially surrounding the core portion; a gas pool in contact with the core portion; an air supply pipe in fluid communication with the gas pool; a gap is provided that extends at least partially between the core portion and the outer peripheral portion and does not contact the gas pool; The gas-blowing plug has a tip end surface on which the gap is open and the tip end of the core portion is exposed.

2. The gas injector plug of claim 1 further comprising a metal case at least partially surrounding said outer periphery.

3. 3. The gas blowing plug according to claim 1, wherein the width of the gap is 0.10 mm or more and 0.50 mm or less.

4. A method for manufacturing a gas-blowing plug, comprising: a first step of forming a preform of the gas-blowing plug; and a second step of firing the preform; The first step forming a core portion of the preform using a porous refractory material; forming a peripheral portion of the preform using a dense refractory material; and disposing a combustible material between the core portion and the outer periphery of the preform; the second step includes burning at least a portion of the combustible material; In the step of disposing the combustible material, the combustible material is disposed so as to be exposed on a leading end surface of the preform and not to be exposed on a base end surface of the preform; A method for manufacturing a gas-blowing plug, wherein a void formed by burning off the combustible material is open on the tip surface of the gas-blowing plug, and the tip of the core body portion is exposed.

5. 5. The method for manufacturing a gas-blowing plug according to claim 4, wherein the combustible material is in the form of a wire, a rod, a sheet, or a combination thereof.

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